A suicide car bomber hit worshippers leaving a Shia mosque in the town of Tuz Khormato shortly after midday prayers on Friday, killing at least 10 people and wounding 21 others, police said.

The blast targeted the Hussainiyat al-Rasoul al-Azam Mosque in Tuz Khormato, 130 miles north of Baghdad.

The attack occurred as Iraq's Sunni-dominated insurgency, including al-Qaeda in Iraq, pressed an 'all-out war' on the country's Shia majority. The spasm of violence began on Wednesday in Baghdad and has spread throughout the country, killing more than 200 people and wounding more than 600 in three days.

In other violence on Friday, gunmen opened fire on day laborers in the capital, killing three and wounding a dozen in a drive-by shooting. The workers had assembled in east Baghdad seeking day jobs.

"We are innocent people...Those criminals and terrorists came and did this to us," said Salah Aziz Ali, a wounded worker.

On Thursday, suicide bombers killed at least 31 people in three suicide attacks targeting Iraqi police. A day earlier, at least 167 people were killed and 570 wounded in more than a dozen bombings in Baghdad. The largest toll resulted from a suicide bombing against day laborers in the largely Shia Kazimiyah neighborhood in north Baghdad.

The US military continued attacks on militant strongholds in western Iraq along the Syrian border where militants hold many towns and villages along the Euphrates River as it flows southeastward from the Syrian border.

Al-Qaeda in Iraq said the brutal bombings in Baghdad were reprisals for the joint Iraqi-US operation that pushed insurgents out of their stronghold in Tal Afar, also near the Syrian border but in the far north of Iraq.

The American military said US jets pounded an abandoned school used by al-Qaeda in the town of Karabilah, about 200 miles northwest of Baghdad. Nine insurgents were killed in the Thursday night strike.

Before dawn Friday, US jets were called in again to destroy what the military said was a bomb factory in Haditha, also along the Euphrates in western Iraq.

Two days earlier the al-Qaeda leader in Iraq, Abu Musab al-Zarqawi, vowed to wage an 'all-out war' on the country's Shia majority, calling its members collaborators of the 'Jews and Crusaders'.

At Al-Kindi Teaching Hospital, where the laborers were taken after Friday's drive-by shooting, the wounded lined the corridors, while others lay on gurneys as doctors worked frantically to stanch bleeding and bandage wounds.

A car bomb also detonated near an Iraqi police patrol in the town of Haswa, near Baghdad, killing three officers and wounding four, police Captain Muthana Khalid said.

In the Iskandariya district, 30 miles south of Baghdad, gunmen broke into the house of the local mayor and shot him to death, after first killing his four bodyguards, police Khalid said.

In the capital's Shia district of Sadr City, gunmen assassinated Sheik Fadil al-Lami, the cleric at Imam Ali mosque, as he waited to fill his car with gas, said police Lieutenant Colonel Shakir Wadi. Wadi said police also discovered the bodies of three people in the district, one an Iraqi soldier.

The US. military also said on Friday, a Marine had been killed near the town of Ramadi, the volatile capital of Anbar Province that stretches west from Baghdad to the Syrian, Jordanian and Saudi borders.

The spike in violence, US and Iraqi officials said, was not surprising. It was viewed as a campaign by the Sunni-dominated insurgency to derail the political process and the Oct. 15 referendum on the draft constitution. Sunnis, once the power brokers under Saddam Hussein's regime, complain that the draft charter heavily favors Iraq's Shiite and Kurdish populations.

"These spikes of violence are predictable around certain critical events that highlight the progress of democracy," said Major General Rick Lynch, the chief American military spokesman.

Lynch said the joint Iraqi-American force of 8,500 killed 145 insurgents and captured 361 in the second operation in a year to rid Tal Afar of militants, including foreign fighters crossing from Syria.

Iraqi and US officials say the fighters sneak across the porous border and have accused the Damascus government of doing little to stop the influx. While Syria has repeatedly denied the charges, Iraqi officials have adopted an increasingly stronger tone and the country's defense minister has pledged that operations targeting the militants would be extended to other Euphrates River valley towns seen as militant safe havens.

"We will not retreat or be silent. There will be no room for you (insurgents) in all of Iraq. We will chase you wherever you go," Defense Minister Sadoun al-Dulaimi, a Sunni, told reporters.

For the Iraqi leadership, the challenge has been to ward off a seemingly endless insurgent campaign while winning the support of the country ahead of the referendum and the trial of Saddam just days later. Some leading Sunni Arab groups have condemned the attacks against civilians.

And the Iraqi government, trying to deflect an escalation of Sunni-Shia sectarian tensions, has stressed that foreign fighters are behind much of the worst violence, pointing to the arrest of a Palestinian and a Libyan in Wednesday's Kazimiyah attacks on day laborers. The bomber, they said, was Syrian. The government gave no evidence to support those claims.

The massive bombings took place with both Iraqi President Jalal Talabani and Prime Minister Ibrahim al-Jaafari in the United States.

"Today, Iraq is facing one of the most brutal campaigns of terror at the hands of the forces of darkness," Talabani said Thursday, addressing the United Nations General Assembly with an appeal for international help.